There has been proposed, as a piezoelectric actuator device having a large displacement value, a cantilever-mounted piezoelectric bender which comprises an elongated plate-like piezoelectric actuator member including piezoelectric ceramic layers and electrodes therein. The actuator member is supported at one end thereof by a support, whereby a substantial amount of displacement can be obtained at the free end of the member. See for example U.S. Pat. Nos. 5,023,503 and 5,068,567. This kind of piezoelectric actuator device is disadvantageous, however, in that its application is limited since a support is needed to mount same and in that the force generated is rather small. A piezoelectric actuator device operable without a support is also known which comprises a piezoelectric actuator member to which a metal sheet is bonded so that the displacement of the actuator member is amplified by the metal sheet. However, this type of actuator device is rather complicated in structure and cannot easily be manufactured at low costs.
It is therefore an object of the present invention to provide a piezoelectric actuator device which has a large displacement value.
It is another object of the invention to provide a piezoelectric actuator device which can transmit its output without the need for a dedicated support.
It is a further object of the invention to provide a piezoelectric actuator device which is relatively simple in structure and can therefore be manufactured at lower costs.